CN106768171A - Deep cooling medium liquid level determining approach in space propultion - Google Patents
Deep cooling medium liquid level determining approach in space propultion Download PDFInfo
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- CN106768171A CN106768171A CN201510801439.9A CN201510801439A CN106768171A CN 106768171 A CN106768171 A CN 106768171A CN 201510801439 A CN201510801439 A CN 201510801439A CN 106768171 A CN106768171 A CN 106768171A
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- signal
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
- G01F23/26—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields
- G01F23/263—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields by measuring variations in capacitance of capacitors
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Electromagnetism (AREA)
- Thermal Sciences (AREA)
- Fluid Mechanics (AREA)
- General Physics & Mathematics (AREA)
- Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
Abstract
For the deep cooling medium liquid level determining approach in space propultion, belong to Aerospace test technical field, including the coaxial capacitance sensor in deep cooling medium storage tank, the transmission circuit outside storage tank and connection sensor, the signal connecting line of transmission circuit；Coaxial capacitance sensor includes being placed along liquid level change direction, and concentric, fixed intervals metal inner pipes, metal outer pipe are kept each other；Signal connecting line is made up of inner wire, middle conductor, outer conductor；Signal transmitting circuit is made up of the detection unit of the signal source with common reference point, the impedance transformer of the subsidiary capacitive effect of elimination connecting line and output response liquid level variable quantity.This invention ensures that the linear relationship between sensor capacitance and liquid level in space propultion application is set up, certainty of measurement is improved, and save extraction and arrangement number of cables, space and weight.
Description
Technical field
The invention belongs to Aerospace test technical field, it is related to a kind of deep cooling medium liquid level determining approach in space propultion.
Background technology
In space flight propulsion field, the precooling such as the carrier rocket such as liquid hydrogen, liquid oxygen low temp fuel and liquid helium, liquid nitrogen, supercharging
Obtained with the accurate liquid level information of cryogenic media, had very important significance.
Liquid level sensor based on condenser type principle has energy low, and response is fast, can continuously measure, the features such as no-movable part,
There is unique advantage for above-mentioned application.Existing disclosed such liquid level detection technology, still suffers from certain defect or deficiency, it is difficult to
Meet the deep cooling medium level gauging in space propultion.
A kind of coaxial-type direct capacitance is disclosed in the existing Y of public technology CN 2700847 " transducer for liquefied natural gas level meter "
Liquid level sensor, it forms direct capacitance to be measured using inner cylinder and outer tube structure, and inside and outside electrode connects the heart yearn of signal cable respectively
With the structure of screen layer.Because electronic component can not possibly be in cryogenic environment, it is necessary to which detection circuit is placed on outside deep cooling tank.
Obviously, the heart yearn in this capacitor sensor structure with shielding interlayer exist numerical value it is larger and with the factors such as temperature, position become
The subsidiary electric capacity changed, the unstable electric capacity is superimposed upon on sensor capacitance to be measured, causes not eliminable error.For liquid helium
(1.048), the space propultion deep cooling medium of the low relative dielectric constant such as liquid hydrogen (1.233), the cable in actual arrangement is long in addition
Degree is often up to tens of rice, and above-mentioned influence is more serious, or even exceeds well over actual capacitance change to be detected, it is impossible to meets and requires.
Disclosed in application in 201210250511.X " segmentation capacitor liquid level sensor measuring circuit implementation method ", for adopting
Take that sub-structure, complexity be high, capacitance sensor that is having been influenceed on reliability, by specific sensor electrode connected mode
With the guarantee of device operational characteristics in pre-amplifier unit, though can be to the harmful effect of the subsidiary electric capacity of connecting line effectively, for one
The measurement of individual sensor capacitance to be measured, it is obviously desirable to be equipped with two independent signal cables, it is difficult to meet right in space propultion application
In the strict limitation requirement for drawing and connecting up the aspects such as quantity, space, weight.
The content of the invention
The present invention is in view of the shortcomings of the prior art, provide a kind of deep cooling medium liquid level determining approach in space propultion.
The present invention uses following technical scheme to achieve the above object：
Deep cooling medium liquid level determining approach in space propultion, including coaxial capacitance sensor in deep cooling medium storage tank,
Transmission circuit and connection sensor, the signal connecting line of transmission circuit outside storage tank；Coaxial capacitance sensor is included along liquid
Position change direction is placed, and concentric, fixed intervals metal inner pipes, metal outer pipe are kept each other；Signal connecting line by inner wire,
Middle conductor, outer conductor and insulating materials are constituted；Signal transmitting circuit, by the signal source with common reference point, eliminates connecting line
The impedance transformer of subsidiary capacitive effect, detection unit composition；Wherein, signal connecting line inner wire is connected in sensor side and sensed
Device metal inner pipe, the inner wire other end is acted on by the signal source of transmission circuit and connects impedance transformer input；Middle conductor is being passed
Sensor connection end floating, other end connection signal transmitting circuit middle impedance converter output；Outer conductor connects metal in sensor side
Outer tube, outer conductor other end connection common reference point；The electricity parameter of detection unit output response liquid level change；
Inner wire is surrounded by middle conductor, is separated by inner insulating layer between inner and outer conductor, and middle conductor is surrounded by outer conductor, in,
Separated by external insulation layer between outer conductor；
Common reference point is the common signal ground of signal source, impedance transformer, detection unit use.
Inner insulating layer, the chosen material of external insulation layer are polytetrafluoroethylene (PTFE).
The difference of the interior diameter of metal outer pipe 2 and the overall diameter of metal inner pipe 1 is maintained between 2.0mm to 5.0mm；
Impedance transformer output signal is identical with effect pumping signal amplitude size in the conductor, frequency, phase；
Detection unit output response liquid level change electricity parameter include alternating voltage, DC voltage, DC current signal,
Any one of frequency signal.
Beneficial effects of the present invention：
First, do not influenceed by signal connecting line length and shape, temperature change, improved certainty of measurement and stability；2nd, may be used
It is used for existing measurement apparatus as standalone module, realizes performance improvement.3rd, save and draw and arrangement number of cables, space and weight
Amount.
Brief description of the drawings
Fig. 1 is structural representation of the invention, including：Conductor in 1 inner tube, 2 outer tubes, 3 inner wires, 4,5 outer conductors,
6 driving sources, 7 impedance transformers, 8 detection units, 9 common reference points.
Fig. 2 is the structural representation of signal connecting line, including：Conductor in 3 inner wires, 4,5 outer conductors, 10 inner insulating layers,
11 external insulation layers.
Fig. 3 is that the principle that sensor liquid level determines is illustrated.
Fig. 4 is that influence of the subsidiary electric capacity to actual measurement is illustrated.
Fig. 5 is a typical instantiation of transmission circuit.
Specific embodiment
The present invention is further described in detail below in conjunction with the accompanying drawings：
As shown in Figure 1, for the deep cooling medium liquid level determining approach in space propultion, including in deep cooling medium storage tank
Coaxial capacitance sensor, the transmission circuit outside storage tank and connection sensor, the signal connecting line of transmission circuit.Coaxially
Capacitance sensor includes being placed along liquid level change direction, and concentric, fixed intervals metal inner pipe 1, metal outer pipe 2 are kept each other.
Signal connecting line is made up of inner wire 3, middle conductor 4, outer conductor 5 and insulating materials.Signal transmitting circuit is by with common reference point
9 signal source 6, the impedance transformer 7 and detection unit 8 for eliminating the subsidiary capacitive effect of connecting line are constituted.Wherein, signal connection
Line inner wire connects sensor metal inner pipe in sensor side, and the inner wire other end is acted on by the signal source of transmission circuit, and is connected
Signal source output is input into as impedance transformer；Middle conductor is in sensor connection end floating, other end connection signal transmitting circuit
Impedance transformer is exported；Outer conductor connects metal outer pipe, outer conductor other end connection common reference point in sensor side；Detection is single
The electricity parameter of unit's output response liquid level change.
Metal inner pipe 1 is co-axially mounted with metal outer pipe 2, and fixed intervals are kept each other, forms concentric cylinder capacitor.It is preferred that
The difference of the interior diameter D2 of metal outer pipe 2 and the overall diameter D1 of metal inner pipe 1 is maintained between 2.0mm to 5.0mm, metal inner pipe 1
It is more than 300mm with the length of metal outer pipe 2, electric capacity to be detected and its changing value are relatively adapted to detection, while avoiding impurity accidental short circuit
And ensure that liquid smoothly circulates between inner and outer pipe.
As shown in Fig. 2 signal connecting line has three layers of coaxial configuration, inner wire 3 is surrounded by middle conductor 4, between inner and outer conductor
Separated by primary insulation material 10, middle conductor 4 is surrounded by outer conductor 5, in, separated by outer layer insulation material 11 between outer conductor.Interior,
External insulation layer material is the polytetrafluoroethylene (PTFE) suitable for cryogenic environment.
The coaxial capacitance sensor determined for deep cooling medium liquid level belongs to dielectric constant variable type capacitance sensor, i.e., according to be checked
Top is surveyed for the difference between gas phase media constant and liquid phase medium dielectric constant is detected, principle explanation is carried out in conjunction with Fig. 3.
Metal outer pipe internal diameter is made for b, metal inner pipe external diameter a, the dielectric constant of gaseous medium is k1, and the dielectric of liquid medium is normal
Number is k2, and metal inner and outer pipe effective length, i.e., maximum detection is highly H.Then when liquid level is h, according to becoming, dielectric is normal
Number type capacitance sensor is theoretical, and measuring sensor capacitance Cm can be calculated with following formula：
Clearly for the sensor and testing medium that determine, the parameter such as a, b, k1, k2, H is fixed, and Cm is situated between with liquid
The liquid level h of matter is linear, as long as obtaining the common electric signal with Cm in one-to-one relationship by detection means, such as
The disposable type signal such as voltage, electric current, frequency, you can complete the determination of medium liquid level information.
However, above-mentioned calculating consideration is the sensor effective capacitance for perceiving liquid position change, actual measuring condition is not considered
Under, the influence that the signal connection from sensor to transmission circuit determines to liquid level.As shown in figure 4, size with temperature, position etc. because
Influences of the subsidiary electric capacity Cx of connecting line that element varies to actual measurement is to be in parallel with sensor effective capacitance, i.e., folded with Cm
Plus.So, the linear relationship of script will no longer be set up, and the uncertainty due to Cx in itself, the capacitance signal for detecting also without
Method obtains available liquid level information through treatment.
In Fig. 5, amplifier A1 and electric capacity C1, C2, R1, R2, R3, R4 constitute Wen's sine-wave oscillator.Work as satisfaction
Relation：When R1=R2, C1=C2, R4 >=2R3, A1 can export sine wave signal relative to common reference point, be designated as Vs.
Ripple signal frequency f byCalculate.
The sine wave signal of output sends into the in-phase input end of A2.By the effect of amplifier A2 " virtual short ", homophase input
Terminal voltage is identical all the time with anti-phase input terminal voltage, i.e., equivalent to driving source in A2 inverting inputs and the change power transmission of signal connecting line
Terminal inner wire is connected, that is, is connected with the metal inner pipe of capacitance sensor.Connect the connecting line of capacitance sensor metal outer pipe
The transmission circuit end connection common reference point of outer conductor.
Therefore, electric capacity Cm to be detected is located between the inverting input of amplifier A2 and common reference point, and amplifier A2's is anti-phase defeated
Enter and electric capacity Cs is set between end and output end, then constitute in-phase proportion computing circuit as detection unit.The output voltage of A2 is remembered
It is Vout, then has：
So, the output voltage of detection unit is the sine wave signal with pumping signal same frequency, and amplitude and the linear passes of Cm
System.Due to eliminating the influence of uncertain sized capacitors Cx, i.e. Cx is equivalent to 0, therefore detection unit output signal amplitude in the formula
Linear relationship between liquid level is set up.So far, the usable electricity parameter of the liquid level that met with a response change.If any
Necessity, can also take rectifying and wave-filtering, and this ac voltage signal is further changed into DC voltage, if obtaining frequency through V-F conversion again
Amount, these are the general common techniques known in the industry and easily realize.Such subsequent treatment link is believed that detection unit
Part.
Amplifier A3 selects high speed high current type operational amplifier.The in-phase input end of A3 connects the inverting input of A2, i.e. phase
Introduced when in by pumping signal, and inverting input and output end are connected to form follower.In addition A3 has high speed high current
The guarantee of characteristic, middle conductor it is available with plus pumping signal in the conductor, amplitude size, frequency, phase identical all the time
Signal, the connection line capacitance between middle conductor and outer conductor is intended only as the load of high speed high current type A3 and drives, not to inspection
Survey unit and bring influence.Due in the absence of potential difference, charging and discharging effects not being produced between the inner wire of signal connecting line and middle conductor,
Connecting line capacitor equivalent i.e. between the two is 0.
Above-described is the preferred embodiment of the present invention, it is not limited to this.For example, driving source can also use specialized signal
The mode such as generation chip or direct digital synthesizers is produced.
The present invention is to provide a kind of deep cooling medium liquid level determining approach in space propultion, the realization of its performance improvement has
There is more universal applicability.For personnel in the art, under the premise without departing from the principles of the invention, can make
Some retouchings and improvement, also should be regarded as protection scope of the present invention.
Claims (7)
1. the deep cooling medium liquid level determining approach in space propultion, it is characterised in that：Including same in deep cooling medium storage tank
Axle capacitance sensor, the transmission circuit outside storage tank and connection sensor, the signal connecting line of transmission circuit；Coaxial capacitance
Sensor includes being placed along liquid level change direction, and concentric, fixed intervals metal inner pipe 1, metal outer pipe 2 are kept each other；Letter
Number connecting line is made up of inner wire 3, middle conductor 4, outer conductor 5 and insulating materials；Signal transmitting circuit, by with common reference
The signal source 6 of point 9, the impedance transformer 7 for eliminating the subsidiary capacitive effect of connecting line, detection unit 8 are constituted；Wherein, signal connects
The inner wire 3 of wiring in sensor side connection sensor metal inner pipe 1, the other end acted on by the signal source 6 of transmission circuit and
Connection impedance transformer input；Middle conductor 4 becomes in sensor connection end floating, 4 other ends connection signal transmitting circuit middle impedance
Parallel operation 7 is exported；Outer conductor 5 connects metal outer pipe 2, other end connection common reference point 9 in sensor side；Detection unit 8 is defeated
Go out to respond the electricity parameter of liquid level change.
2. method according to claim 1, it is characterised in that：Described inner wire is surrounded by middle conductor, inside and outside to lead
Separated by inner insulating layer between body, middle conductor is surrounded by outer conductor, in, separated by external insulation layer between outer conductor.
3. method according to claim 1, it is characterised in that：Described common reference point be signal source, impedance transformer,
The common signal ground that detection unit is used.
4. the method according to claim 1,2, described inner insulating layer, the chosen material of external insulation layer are polytetrafluoroethylene (PTFE).
5. method according to claim 1, the difference of the overall diameter of the interior diameter and metal inner pipe 1 of described metal outer pipe 2 is protected
Hold between 2.0mm to 5.0mm.
6. method according to claim 1, the excitation letter of described impedance transformer output signal with effect in the conductor
Number amplitude size, frequency, phase are identical.
7. method according to claim 1, the electricity parameter of described detection unit output response liquid level change includes
Any one of alternating voltage, DC voltage, DC current signal, frequency signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510801439.9A CN106768171A (en) | 2015-11-20 | 2015-11-20 | Deep cooling medium liquid level determining approach in space propultion |
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| CN201510801439.9A CN106768171A (en) | 2015-11-20 | 2015-11-20 | Deep cooling medium liquid level determining approach in space propultion |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107870020A (en) * | 2017-12-26 | 2018-04-03 | 太原理工大学 | A kind of triaxial cable capacity water level measuring device |
| CN113285637A (en) * | 2021-06-01 | 2021-08-20 | 南京工业大学 | High-precision micropipette feedback control system |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107870020A (en) * | 2017-12-26 | 2018-04-03 | 太原理工大学 | A kind of triaxial cable capacity water level measuring device |
| CN107870020B (en) * | 2017-12-26 | 2019-12-17 | 太原理工大学 | Three coaxial cable capacitance type water level measuring device |
| CN113285637A (en) * | 2021-06-01 | 2021-08-20 | 南京工业大学 | High-precision micropipette feedback control system |
| CN113285637B (en) * | 2021-06-01 | 2023-05-26 | 南京工业大学 | High-precision micro-pipetting feedback control system |
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